Which one of the following statement is not valid for aerosols ?

Options

A. They are harmful to human health
B. They alter rainfall and monsoon patterns
C. They cause increased agricultural productivity.
D. They have negative impact on agricultural land

Answer

To determine which statement is not valid for aerosols, let's analyze each option step by step.

### Step-by-Step Solution:

1. **Understanding Aerosols**:
- Aerosols are colloidal suspensions of fine solid particles or liquid droplets in the air. They can originate from various sources, including natural phenomena (like volcanic eruptions) and human activities (like industrial emissions).

2. **Evaluating Each Statement**:
- **Statement 1**: "They are harmful to human health."
- This statement is valid. Aerosols can cause respiratory issues and other health problems when inhaled.

- **Statement 2**: "They alter rainfall under monsoon patterns."
- This statement is also valid. Aerosols can influence cloud formation and precipitation patterns, thus affecting rainfall.

- **Statement 3**: "They cause increased agricultural productivity."
- This statement is **not valid**. Aerosols hinder sunlight from reaching plants, which negatively impacts photosynthesis and, consequently, agricultural productivity.

- **Statement 4**: "They have a negative impact on agricultural land."
- This statement is valid. Since aerosols can reduce sunlight and affect photosynthesis, they can indeed have a negative impact on agricultural land.

3. **Conclusion**:
- The statement that is not valid for aerosols is **Statement 3**: "They cause increased agricultural productivity."

### Final Answer:
The statement that is not valid for aerosols is: **They cause increased agricultural productivity.**

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